1. Field of the Invention
The present invention relates to progressing cavity pumps and particularly to such pumps suitable for pumping liquid/solid mixtures having a high proportion of relatively incompressible solids.
2. Description of the Prior Art
In, for example, mining applications it is necessary to pump explosive mixtures having liquid and solid components from a truck carrying bulk supplies of the components to pre-drilled holes in the rock to be quarried or mined. Normally the solids content of the mixture is about 35-40% of the total, the remainder being liquid. It is desirable from a cost point of view to reduce the liquid content so that the mixture is about 50% solids. However, existing progressing cavity pumps have excessive power requirements when pumping mixtures of such high solids content and are prone to entrapment of solid material and stalling. Examples of such pumps have been described in U.S. Pat. No. 4,773,834, U.S. pat. No. 4,591,322, GB 1,542,786 and GB-A2,228,976.